Transformer



A. R. DAVIS Oct. 31, 1944.

TRANSFORMER Filed NOV. 24, 1941 4 Sheets-Sheet 1 Oct. 31, A R. DAVISTRANSFORMER Filed NOV. 24, 1941 4 Sheets-Sheet 2 gwn/who@ @www5 A. R.DAVIS TRANSFORMER Oct. 31, 1944.

Filed Nov. 24, 1941 4 Sheets-Sheet 5 u YIIIIIIIIIIIII 'lll/III,

Oct. 31, 1944. A` R, DAV|5 2,361,384

TRANSFORMER Y Filed Nov. 24. 1941 4 Sheets-Sheet 4 Il /1 s: j

Patented Oct. 31, 1944 U NLT E D STlli'll-iiil PAT EN T Q'FJFQEC E'TRANSFOBMER Ariel R. Davis, ProvolUtah Application November 24, 1941,Serial No. 420,286.

1 Claim.

M;O invention relates` to an improved method of controlling lights, orelectrical apparatus of anytype requiring a; variable A. C. voltage onsingle.` on multiple circuits.

A further object is to provide a device that can be adjusted to anylpoint within the range of device from above the full line voltage tozero ozrsingleY or multiple circuits.

A still further object is to provide a new transformer and brush`combination, which through the. use` of various simple improvementsprevents the usual. internal losses and.heating of windings-due to theshort circuitingl of adjacent turns by the usual typeotbrush., making atransformer ofi high efficiency which will last longer and give greatersatisfaction without any of the usual troubles in operation andmaintenance.

A: stillA fur-therobject is to provide a dinner fon multiple circuits,which ris controlled by linger operated sliders so arranged that theymay be worked individually. or in unison as the time and ciccumstance.requires;

The. essential feature of the invention is an electrical; control devicefor raising and lowering.the voltage through a continuous range Withcut4circuitv interruption on single or multiple circuits. The principle bywhich the continuous voltage is( maintained is thatthere are twocontactors on each brush insulated from each other and arrangedin such aposition andY mechanically connected together in such a.. manner thatthey,y contact oneturn or two adiacent turns-of the transformer windingat all times. In other words-.this isean autofv transformer designed foruse.` to control. electrical circuits by raising or lowering voltage.to. any given. load. such. as a motor, .bank` of lights, electricfurnace, and the Witltthis. devicel there is short circuiting betweenthe. turns oi.-` the main transformer windings when` a. brushiscwerlanpilh; any two adiant turns.. When the brush is overlapping tivoadjacent turns,l the difference in potential ia correctedby connectingone side of the brush wftlione endl of a singleturn of'wiie wound on thecore andv wound in the same direction as the. windingx the particularbrush contacts. The other endof this. single turn is connected to onelad oil the primary. winding, of an auxiliary transformer. The other endof the primary winding is tl'ien` connected back to the other side ofthebrush. Inrtlle secondary winding of this auxiliary transformer there is`a resistance in serieswith. thewinding. It. ls combination of, devicesthat prevent-.albany short' circuiting. in

Ulli-1119) the main windings. For eadiseparate circuit there has to be aseparate brush with its own separate turn and auxiliary transformer. It.is this improved relationship of devices that make it possible to useamultlple number of sliderson a single winding. and yet have no shortcircuiting of the winding, for each circuit takes care of its own localvexciting current.

The winding of the transformer can be of the auto-transformer type, orwith a primary and secondary winding. These windings are madein suchamanner that. the brush can con tact eachV individual turn used` in thevoltage regulation by passing over it. Where a primary and secondarywinding. is used, the secondary winding may be extra heavy, and. of` fewturns where a heavy current. is. to be regulatedv with only a smallrange` in the voltage. The autotransformer type of winding in most casesis the desired type of winding because ofsimplicity and lower cost ofmanufactureetc.

The shape of the core would' determine to a great extent the generalshape of the windings and the building of. efficient transformer.

The three general shapes of cores usedV for transformers are the core,4shell;` and toroidal. The core type would be the most useful for mydevice because a separate Winding can be placed on one or more legsthereby increasing the external surface,. thus making possible a greaternumber of sliders for voltage regulation.

Where circular motion is desired, a toroidal coll maybe used with asingle. brush of the af'ore mentioned type ony an arm and revolved aboutthe axis of the toroid. The shell type of transformer may be employed inmy device where both at primary and secondary winding are used with thebrushes, making contact with the secondary.

For easy and effective operation when more than one Winding is used; forthe slidersrto contact, it isdesirabletohave. all the slidersat one endof the transformer when they are at full voltage, and the other end whenat no voltage. In order to do this the windings are wound with a correctpolarity in the manner they will be connected together, which would bein either series or parallel, for single phase currents; and eitherdelta or star, for three phase currents.

It is often desirable to raise thevoltage above the line voltage. To. dothis, extra turns are put on each leg above where the linevoltage isapplied. The number of extra turns will raise the voltage in a directratio to the number of turns on the rest of the connected coil.

These objects I accomplish with the device illustrated in theaccompanying drawings ln which similar numerals and letters of referenceindicate like parts throughout the several views and as described in thespecication forming a part of this application and pointed out in theappended claim.

In the drawings in which I have shown my device,

Figure 1 is a plan view of the transformer.

Figure 2 is a side elevation of Figure l.

Figure 3 is an end view of Figure l.

Figure 4 is a diagrammatic view of the wiring system used in thetransformer.

Figure 5 is a section on line 5-5 of Figure 6.

Figure 6 is an enlarged end view of one of the brushes.

Figure 7 is a diagrammatic showing of the contacts of a brush engagingthe windings of the transformer.

Figure 8 shows the next advanced position of the brush from that shownin Figure 7.

Figure 9 shows the brush in its next relative position.

Figure l0 shows the last position of the brush before again entering theposition shown in Fig ure 7.

Figure ll is a diagrammatic showing a modication of the inventionmodified to show toroidal transformer.

This invention primarily would be used for stage lighting installationsto control the various lights on the stage border and other pointsdesired, but is just as important and pertinent to other types ofvoltage regulating transformers for industrial uses.

`The transformer is made of a rectangular core having two legs 5 and 6around which the windings B and C are wound. The windings B and C arecontinued toward one end of the transformer core beyond the point wherethe lines 1 and B are tapped onto the windings, providing extra windingswhich are utilized so that brushes do not come to rest on a blank space,but provides extra windings which may be utilized when required tocorrect line voltage drop by stepping up the voltage above the operatingvoltage of the line.

The linger control brushes are made of two contact strips 9 and I0spaced apart by insulation 4. The two brushes are connected to andlongitudinally operated along the slider and current carrying bus bars Hand I2. One of these bars Il is connected to the load L, shown as aseries of globes 2li and thence through the common ground wire I3 to thealternator G.

The transformer is made with an elevated non-conductor block 23 at eachend thereof in which the ends of the two bus bars II and I2 aresupported and carried and springs 24 are mounted on the top bar II tolimit the endward movement of the brushes so that they will always be onthe windings of the transformer and will never pass too far over theends of the windings of the transformer.

The brushes are all alike, so I will describe but one. Each brushconsists of a main body block 25 of non-conducting material, and thisblock is bored transversely to receive the bus bars II and l2 to permitthe brush to be moved 1ongitudinally along said bars. The top of eachbrush is fiat and carries a vertical strip 26 secured therein bysuitable locking bars 21. On the top end of the strip I provide a fingercontact block 2B secured in a like manner to the strip. This thin stripis made to allow a cover to be placed over the entire transformer ifdesired, and at the same time permit the finger operation of the brusheswithout any danger of the operator getting a shock through carelessness.Each of the holes through the block 25 is enlarged from one side toreceive a contact sleeve 29, which sleeve 29 is to pass contact to thebar from the brushes. This is accomplished by the following means:

The contact brushes 9 and I0 are formed by takeng two at metal strips,such as copper, bending them back upon themselves to form outwardlyextended legs 30 and vertical legs 3|. The two brushes are spaced apartby an insulating strip 33 and the assembly of two parts of the brush andthe insulation strip is set in a vertical slot 34 of block 25. Each leg30 of the brush is provided with an insulation base 35 to insure that nobending or breaking of the brush will engage the surface of the windingoi' the transformer and cause a short circuit. The depending ends 35 ofbrushes engages the surface of the winding B or C. The width of thedepending ends 36 being such that neither one will be as great as thewidth of the insulation between the winding of the transformer, and thewidth of the two so spaced that one will always make contact with a turnof the winding. Tension springs 37 are set in sockets in the block 25and press down upon the top side of each leg 30 of the brushes to insurean even pressure on the winding of the transformer. A exible lead 38 issecured to the leg 3l! of the brush l0 on one end and the other endconnected to the plate all on the end -of sleeve 29. 'Ihe leg 30 of thebrush 9 is connected to a plate 4I on the end of the other sleeve 29 bythe flexible lead 42. The plate 4| is made with a hole 43 therethrougharound the bar l2 to insure that there will be no short circuiting ofthe two slider bars Il and i2. As shown in Figure l, there are amultiplicity of these bus bars and an equal number of linger controlledbrushes and their relative positions shown in Figure l show thepositions of any given four of these brushes and illustrates that anyposition desired for any given circuit may be obtained without effectingany of the other circuits, each being utilized as an independent dimmeralthough they all operate on the same transformer.

The auxiliary transformer T is shown as a primary winding I5, asecondary winding I1 and a resistance R connected with the Vsecondarywinding. The bar Il is connected to one nd of a single turn winding I 3wound around the en'd of the core A, in the same direction as thewinding which the brush contacts, and thence out to the primary windingI5 of the auxiliarytransformer f1* to the circuit. The auxiliarytransformerT" is wound with the correct number of turns so that it willlimit the current, when the single turn is short circuited, to a smallvalue. but when the full load current is passing through it, thereactance is very small, having no appreciable effect on the load. Thevalue of the resistance R is 'adjusted to give the minimum loss when themaximum load current 'is passing through the transformer T, which lossis a very small value. It will be obvious that for each slider or vbrushand circuit connected thereto there must be a separate single turn I8and an auxiliary transformer T. rIn the diagrammatic view shown inFigure 4, I'have shown four different individual brushes with fourindividual loads L, with each brush provided with its individual singleturn I8 and the 4corresponding individual auxiliary transformer T.`These brushes are also set to show the cycle of operation a single brushas it passes through from one turn to the next of the Windings, however,to show this more clearly Figures '7, 8, 9, and 10 show the relativepositions of a brush as it passes across the length of the transformerwindings. In order to get the proper position for the relativeadvancement of a single brush, these brushes shown in Figure 4 are notshown spaced the same distance apart, as in this type of showing it isnecessary to show the contacts in such relative positions as they willmake when in actual operation over the surface of the transformerwindings.

Figures 7 to l0 inclusively show the relative positions a single brushwill have to the windings of the transformer, and these positions arealso the positions shown in Figure 4 for the four brushes shown therein.

In position I shown in Figure 7, the brush is shown with one side orcontact il engaging one winding of the transformer, while the other sideor contact Ill is over an insulated area. In this position the currentpasses through the brush 9, through the bar Il to the load L. As thebrush advances to the position shown as position 2 of Figure 4 or inFigure 8, the contact III engages an advanced Winding of the transformerwhile the contact 9 is still on the first Winding, thus two windings arecontacted at the same time by the two side contacts 9 and I0. Thedifference in potential is equalized in this position by the single turnI8, which is Wound in the same direction as the winding on which thebrush is contacting; the transformer T having no effect upon thecircuit. Approximately half of the load or current passing through eachside of the brush and out to the load L, shown as the series of 'globes20. As the brush advances to its next position 3, shown in Figure 9, thecontact Ill is still contacting the same turn of the Winding while thecontact 9 is now over an insulated area. In this position the contactIll carries the current through the bar I2 to the single turn I8,through the transformer T, back to the bar I I and out to the load L. Inthis position the reactance in the transformer T is very small, so thatthe current passes readily to the load L. As the brush advances toposition 4 of Figure 10. both of the contacts 9, and Ill ride on asingle winding of the transformer causing a short circuit in the singleturn I8. The current passes through both contacts, the one side goingdirectly to the load, the other through the single turn, the transformerT, and out to the load. The transformer limits the short circuitingcurrent to a small value and dissipates it as heat through theresistance R, utilizing the effect of the auxiliary transformer T andthe single turn I3 to the fullest extent, keeping all heating out of thewinding of the transformer. This cycle is completed and repeated througheach successive movement of the brushes over each successive turn.

A carbon brush or other type of brush having high resistance may be usedinstead of brush shown in Figures 5 and 6 to limit the current whenpassing from one winding to the other, eliminating the use of the smalltransformers and the single turn on a multiple slider installationswhere the device is only to be used for dimmers for lighting circuitswith multiple nger control; but such use causes a heating effect in thewindings of the transformer, which is an undesirable feature as is wellknown in the art.

A choke coil or coils could be used in place of the single turn ortransformers, but with a multiple number of sliders, the heating effectin the main winding would become larger and larger when two or moresliders engage the same turn of the winding. This is mentioned so thatfor some installation, if required by specifications, such aninstallation may be made without departing from the principle of themultiple brush contacts on a single transformer winding and individualfinger control of any circuit.

It will be obvious that various modification and variation may be madein the structure of the device without departing from the spirit of theinvention or the scope of the claim.

The operation of the device is obvious from the above description.

Having thus described my invention, I desire to secure by Letters Patentand claim:

A transformer comprising a core; a main winding on said core; amultiplicity of independently operated, individual circuit load controlbrushes mounted to operate longitudinally along the surface of said mainwinding, making continuous contact therewith; a multiplicity of singlewindings each being of the same potential as one complete turn of themain Winding, each being connected in series with an auxiliary currentlimiting transformer and connected to one of the individual controlbrushes so that the single winding is either in parallel with the turnsof the main Winding when the brush is covering adjacent turns, that arebeing traversed, or forms a closed circuit Within itself at such timesas any brush is completely contacting a single turn of the main winding,said auxiliary transformer limiting the current in the single winding.

ARIEL R. DAVIS.

